Lighting units are used in many areas including areas containing explosive gases and vapors (e.g. areas rated as Class 1, Division 2, and Zone 2 areas). A lighting unit typically includes a housing, a lamp attached to the housing, and a transparent or translucent enclosure attached to the housing and surrounding the lamp. Gases and vapors can enter the housing and enclosure through voids in exterior and interior walls of the housing. Also, heat from the lamp can migrate into the interior of the housing. Users often apply sealants to voids in the exterior walls of the housing to prevent gases and vapors from entering the housing and the enclosure.